mysql将列值变列名 mysql改列类型

SELECT   
  CONCAT(  
    'alter table ',  
    table_name,  
    ' MODIFY COLUMN ',  
    column_name,  
    ' float  DEFAULT NULL;'  
  ) AS col,  
  TABLE_NAME,  
  COLUMN_NAME,  
  DATA_TYPE   
FROM  
  INFORMATION_SCHEMA.columns a   
WHERE TABLE_SCHEMA = 'prod_db' -- 代表所在的数据库  
  AND data_type IN ('double') -- 批量修改的类型